What is the most easily absorbed magnesium formulation?

Magnesium Formulation Bioavailability: Which Is Most Easily Absorbed

Magnesium citrate is the most easily absorbed magnesium formulation, showing superior bioavailability compared to other magnesium preparations. This is supported by research demonstrating that organic magnesium salts have better absorption than inorganic compounds 1, 2.

Bioavailability of Different Magnesium Formulations

Organic vs. Inorganic Magnesium Salts

• Magnesium citrate: Shows the highest bioavailability in controlled studies
• Magnesium glycinate/bisglycinate: Good bioavailability due to amino acid binding
• Magnesium malate: Good absorption as an organic salt
• Magnesium acetyl taurate: Shows good brain penetration 2
• Magnesium oxide: Poor bioavailability (only about 4% absorption) despite having higher elemental magnesium content 3, 4

A randomized, double-blind study specifically found that magnesium citrate led to the greatest mean serum magnesium concentration compared to other formulations following both acute and chronic supplementation 1. After 60 days of supplementation, magnesium citrate resulted in significantly higher urinary magnesium excretion and salivary magnesium concentration compared to magnesium oxide and other formulations.

Factors Affecting Magnesium Absorption

The bioavailability of magnesium is influenced by several factors:

1. Formulation type: Organic salts (citrate, glycinate, malate) are generally better absorbed than inorganic salts (oxide, hydroxide) 4, 5

2. Dosing strategy:

   • Smaller, divided doses throughout the day improve relative absorption compared to a single large dose 5
   • Taking magnesium at night when intestinal transit is slower may improve absorption 4

3. Solubility: More soluble forms tend to be better absorbed

4. Individual factors:

   • Renal function (avoid in creatinine clearance <20 mg/dL) 6
   • Gastrointestinal health
   • Current magnesium status

Newer Formulations

Recent research has investigated novel delivery systems such as Sucrosomial® magnesium, which showed increased bioavailability compared to standard formulations in both ex-vivo and human studies 7. This formulation demonstrated faster absorption rates and higher magnesium concentration in blood, urine, and red blood cells compared to magnesium oxide, citrate, and bisglycinate.

Clinical Implications

When selecting a magnesium supplement:

• For general supplementation: Choose magnesium citrate for optimal absorption
• For those with sensitive GI systems: Consider magnesium glycinate, which may cause less gastrointestinal distress
• For constipation management: Magnesium oxide at 1.5 g/day has been studied, though lower doses of 500 mg to 1 g/day are often used in clinical practice 6
• For neurological benefits: Magnesium acetyl taurate may offer better brain penetration 2

Cautions and Monitoring

• Avoid magnesium supplements in patients with significant renal impairment (creatinine clearance <20 mg/dL) due to risk of hypermagnesemia 6
• Monitor serum magnesium levels periodically, especially in patients taking supplements long-term
• Be aware that higher doses of any magnesium formulation can cause diarrhea due to the osmotic effect in the intestinal lumen 4

In conclusion, while multiple factors affect magnesium absorption, magnesium citrate consistently demonstrates superior bioavailability compared to other commonly available formulations and would be the recommended choice for most individuals requiring magnesium supplementation.